Powder paints containing aluminum and nickel I

ABSTRACT

Improved powder paint compositions employing particulate metal color producing components comprise a unique combination of (a) aluminum flakes individually encapsulated in a thin, thermosettable, organic film-former, (b) nickel powder, and (c) the principal film-former of the powder paint composition in particulate form. The encapsulated aluminum flake is prepared by intimately dispersing the aluminum flake in a solution of the thermosettable, organic film-former of controlled concentration and spray drying the resultant dispersion. In the preferred embodiment, the principal film-former of the powder paint composition is also a thermosettable material and, in the most preferred embodiment, it is also crosslinkable with the thermosettable coating on the aluminum flakes.

RELATION TO PARENT APPLICATION

This application is a continuation-in-part of copending U.S. patentapplication Ser. No. 422,473, filed Dec. 6, 1973 under the same titleand now abandoned. This application contains the illustrative examplesof the parent application and additional illustrative examples whereinthe amounts of thermosettable film-forming material deposited on themetal particles prior to their incorporation into a powder paint areabove that illustrated in the parent. The recitational disclosures a tothe same in the body of the specification are conformed to take intoaccount the additional examples.

BACKGROUND OF THE INVENTION

One basic technique for the manufacture of powder coating materials isthe so-called fusion method. This involves the mixing of solvent-freeraw materials in their molten state, usually via some form of extruder,cooling, pulverization and size separation-classification. This methodhas a number of disadvantages unrelated to pigmentation and anadditional short-coming when metal flakes are employed as pigments. Thehigh shear employed in the mixing stage results in deformation of themetal flakes. Additionally, during the pulverization step, the metalflakes are further deformed and reduced in particle size. Coatingsproduced from such powders are characterized by a low level ofbrilliance and poor polychromatic appearance.

Another basic technique for the manufacture of powder coating meterialsis the so-called solution-preparation, solvent-separation techniquewhich can be effected by more than one method. This general techniqueinvolves the preparation of a coating material in an organic solvent,separation of the solvent from the paint solids, and size-separationclassification. Also, pulverization in some form may or may not berequired depending upon the solvent separation method involved.

The separation of the solvent can be carried out by conventional spraydrying techniques or by heat exchange separation wherein the componentsof a paint solution are separated by volatilization of the more volatilesolvent and separation of the volatilized solvent from thenonvolatilized paint solids by gravitational forces. Since the metalflakes can be added after pulverization, if pulverization is requiredwhen using any of the solvent separation methods, damage to the metalflakes during pulverization can be avoided by using the solutionpreparation, solvent-separation technique. Problems do arise, however,with respect to distribution and orientation of the metal flakes whenthe powder coating material is applied to the substrate to be coated.This is particularly true when the method of application is that ofelectrostatic spray, the method most commonly employed to apply thefinal coating of paint to automobiles and a variety of other metalmanufacturers. In such applications, the flakes tend to orient in arandom fashion with a low percentage of the flakes parallel to thesubstrate. The net result is a high degree of metal protrusion withlittle metallic brilliance and a low gloss factor.

Thus, when either of the aforedescribed methods are used to producemetal-pigmented, powder-paint coatings in accordance with the prior artprocesses, a substantially higher aluminum to non-metal pigment ratio isrequired, relative to the same ratio in liquid paints, in order toachieve the same degree of brightness and metallic appearance obtainedwith liquid paints. Further, the problem of metal flake protrusionremains even when brightness and metallic appearance are achieved.

In liquid paints, it is known to partially coat aluminum flakes used aspigments to increase the electrostatic spray efficiency of such paints.In U.S. Pat. 3,575,900 a method is disclosed for precipitating the resinof the solution coating upon the aluminum flake in colloidal form. Thissolution is then used as such or mixed with another solution for use.The patentee specifically points out that, while it may be convenient tocall this encapsulation, it is not intended to denote that the aluminumparticles are completely eveloped. The resin disclosed for this purposeis a copolymer of vinyl chloride and monoethylenically unsaturatedmonomers containing about 60 to about 99% by weight vinyl chloride.Aluminum flake is also partially coated in U.S. Pat. 3,532,662. Here thecoating was carried out with a random copolymer of methyl methacrylateand methacrylic acid adsorbed on the pigment. By this method, adispersion is made of the solid particles in a liquid continuous phasecomprising an organic liquid containing in solution a polymer which isadsorbed by the particles and a stabilizer, and modifying the polarityof the continuous phase so that the polymer is insoluble therein, thestabilizer being a compound containing an anchor component which becomesassociated with the adsorbed polymer on the particle surface and apendant chain-like component which is solvated by the modifiedcontinuous phase and provides a stabilizing sheath around the particles.It is alleged that this improves the "wetting" of the treated particlesby the film-forming material dispersion-type coating composition.

Powder paints have certain advantages over conventional liquid paints inthat they are essentially free of volatile solvents but they alsopresent problems which differ from the problems encountered with liquidpaints. These differences include differences with respect to employmentof aluminum flakes as a color producing component. For instance, whenflakes partially coated by resin precipitate are employed in liquidpaints, there remains the organic solvent and other components of thesolution to prevent direct exposure of the flake to the atmosphere andother external influences. Further, in powder paints, if aluminum flakeis coated, the coating must be a relatively dry solid and the size,weight and continuity of the organic encapsulation are all factors inaffecting the distribution of such particles when electrostaticallysprayed with the powder that is the principal film-former of the coatingcomposition.

Coated aluminum flakes, i.e., aluminum flakes individually encapsulatedin a continuous thermosettable film, admixed with the particulateprincipal film-former of a powder paint and electrostatically sprayed ona metal substrate will in a substantial portion orient in parallelrelationship to the substrate. This substantially reduces or eliminatesflake protrusion. Unfortunately, however, there remains a tendency forthese coated flakes to assume a substrate-parallel orientation close tothe outer surface of the cured coating. This can produce two undesiredresults. The first of these is the insufficient appearance of metallicdepth in the coating wherein the metal flakes are seen through varyingdepths of a film which is usually colored with a non-metal colorproducing component. The second is an undesired "silvery" effect whichdominates the non-metal color producing component if the concentrationof the near-surface, substrate-parallel flakes is too high.

THE INVENTION

A dominance of silvery effect in polychromatic finishes resulting froman overabundance of aluminum flake near and parallel to the outersurface of a cured coating is avoided and depth variation for the metalcolor producing component in polychromatic or monochromatic finishes isachieved by including in a powder coating composition a combination of(1) aluminum flakes encapsulated in a thin, continuous, coating ofthermosettable, organic film-former and (2) nickel powder.

The nickel powder used as the second metal color producing componentdoes not require encapsulation. Suitable nickel powder for use asparticulate pigment is available from a variety of sources. Advisedly,this powder is of a size that will pass through a 400, preferably a 325,mesh screen or finer. The nickel powder is ordinarily in the form offlakes.

Aluminum flakes which are incorporated in powder paints to provide ametallic color producing component are herein encapsulated in a thin,continuous, thermosettable organic coating through which the aluminumparticle is visible to the human eye. This coating is preferablytransparent but may be translucent. The term "substantially transparent"as used herein means materials which are either transparent ortranslucent or partially transparent and partially translucent.

As these metal pigments are most frequently used in polychromaticfinishes, the powder coating composition will ordinarily contain atleast one non-metal color producing component. The "non-metal colorproducing component" may be a particulate pigment, dye or tint and maybe either organic, e.g., carbon black, or inorganic, e.g., a metal salt.

In accordance with this invention, the encapsulated aluminum flakes andthe nickel powder are admixed, i.e., cold blended, with the balance ofthe coating material after the principal film-former is in particulateform. The encapsulated flakes may be admixed before, after orsimultaneously with nickel powder. The non-metal color producingcomponent may be admixed with the film-forming powder before, after orduring the addition of the coated aluminum flakes and/or the nickelpowder. In the preferred embodiment, the non-metal color producingcomponent is added before the metal color producing components, i.e.,the coated aluminum flakes and the nickel powder.

The aluminum color producing component is most often aluminum flakes inthe form of aluminum paste. To avoid unnecessary complication of thedescription of this invention, such aluminum flakes will be used toillustrate the invention. It should be understood, however, that thismethod is applicable to any particulate aluminum used as a colorproducing component in a powder coating material. This includes aluminumparticles which are solely aluminum, aluminum coated organic particlesand polymer-sandwiched metal particles having exposed metal edges.

Aluminum paste is aluminum flakes, usually about 60 to about 70 weightpercent, in a smaller amount, usually about 30 to about 40 weightpercent, of a liquid hydrocarbon solvent which serves as a lubricant,e.g., mineral spirits. A small amount of an additional lubricant, e.g.,stearic acid, may be added during the milling operation which producesthe aluminum flakes. Everett J. Hall is credited with originating themethod of beating aluminum into fine flakes with polished steel balls ina rotating mill while the flakes are wet with a liquid hydrocarbon. SeeU.S. Pat. No. 1,569,484 (1926). A detailed description of aluminumpaste, its manufacture, flake size, testing, uses in paint, etc. isfound in Aluminum Paint and Powder, J. D. Edwards and Robert I. Wray,3rd Ed. (1955), Library of Congress Catalog Card Number: 55-6623,Reinhold Publishing Corporation, 430 Park Avenue, New York, New York,U.S.A. and the same is incorporated herein by reference.

More specifically, one first disperses the aluminum flakes in about 2 toabout 200 parts by weight of thermosettable film-former per 100 parts byweight aluminum flakes. In one embodiment wherein the coating of suchflakes is relatively light, the aluminum flakes are dispersed in about 2to about 30 weight percent of thermosettable film-former based on theactual weight of the aluminum flakes, i.e., about 2 to about 30 parts byweight of thermosettable film-former per 100 parts by weight aluminumflakes. In most applications, it will be found advantageous to usebetween 10 and 200, preferably between about 30 and about 70, parts byweight of thermosettable film-former per 100 parts by weight aluminumflakes. When metal particles of different density are used, the weightof aluminum flakes of the same surface area can be used to determine theamount of film-former to use in coating the metal particles. When lessthan about 2 weight percent of the film-former is used, completeencapsulation of the metal flakes may not result. When more than about30 weight percent of the film-former is used, care must be taken incontrolling the spray drying operation to minimize the formation of anexcessive amount of spherical particles containing more than one metalflake. The incidence of full coverage is high in the 30 to 70 rangeabove described. Such spherical particles can be removed from the othercoated aluminum flakes by screening. The inclusion of large,multi-leafed particles in a cured coating provides an irregularappearance. A similar result may be obtained if one mixes the uncoatedmetal flakes with the principal film-former of a powder paint while thelatter is in liquid state

The film-former used to coat the aluminum flakes may be aself-crosslinking polymer or copolymer or a chemically functionalpolymer or copolymer and a monomeric crosslinking agent. The preferredfilm-formers for this purpose include thermosettable copolymer systemscomprising: (a) an epoxy-functional copolymer of monovinyl monomers andas crosslinking agent therefor a C₄ - C₂₀, saturated, straight chain,aliphatic, dicarboxylic acid crosslinking agent - exemplified by U.S.patent application Serial No. 172,236 filed August 16, 1971, now U.S.Pat. No. 3,752,870; (b) an epoxy-functional copolymer of monovinylmonomers and as crosslinking agent therefor a mixture of about 90 to 98percent by equivalent weight of a C₄ - C₂₀, saturated, straight chain,aliphatic dicarboxylic acid and about 10 to about 2 percent byequivalent weight of a C₁₀ - C₂₂, saturated, straight chain, aliphatic,monocarboxylic acid - exemplified by U.S. Patent 3,730,930; (c) anepoxy-functional copolymer of monovinyl monomers and as crosslinkingagent therefor a diphenol having a molecular weight in the range ofabout 110 to about 550 - exemplified by U.S. patent application SerialNo. 172,228, filed August 16, 1971, now U.S. Pat. No. 3,758,643; (d) anepoxy-functional copolymer of monovinyl monomers and as crosslinkingagent therefor a carboxy terminated polymer - exemplified by U.S. patentapplication Serial No. 172,229 filed August 16, 1971, now U.S. Pat. No.3,781,380; (e) an epoxy-functional copolymer of monovinyl monomers andas crosslinking agent a phenolic hydroxy terminated polymer -exemplified by U.S. patent application Serial No. 172,225 filed August16, 1971, now U.S. Pat. No. 3,787,520; (f) an epoxy-functional,carboxy-functional, self-crosslinkable copolymer of ethylenicallyunsaturated monomers - exemplified by U.S. patent application Ser. No.172,238 filed August 16, 1971, now U.S. Pat. No. 3,770,848; (g) ahydroxy-functional, carboxy-functional, copolymer of monoethylenicallyunsaturated monomers - exemplified by U.S. patent application Serial No.172,237 filed August 16, 1971, now U.S. Pat. No. 3,787,340; (h) anepoxy-functional copolymer of monovinyl monomers and as crosslinkingagent therefor an anhydride of a dicarboxylic acid - exemplified by U.S.patent application Ser. No. 172,224 filed Aug. 16, 1971, now U.S. Pat.No. 3,781,379; (i) a hydroxy-functional copolymer of monoethylenicallyunsaturated monomers and as crosslinking agent therefor a compoundselected from dicarboxylic acids, melamines, and anhydrides -exemplified by U.S. patent application Ser. No. 172,223 filed Aug. 16,1971; and abandoned in favor of continuation application Ser. No.407,128 filed Oct. 17, 1973 in turn abandoned in favor ofcontinuation-in-part application Ser. No. 526,546 filed Nov. 25, 1974.(j) an epoxy-functional copolymer of monovinyl monomers and ascrosslinking agent therefor a compound containing tertiary nitrogenatoms -- exemplified by U.S. patent application Ser. No. 172,222 filedAug. 16, 1971; (k) a copolymer of an alpha-beta unsaturated carboxylicacid and an ethylenically unsaturated compound and as crosslinking agenttherefor an epoxy resin having two or more epoxy groups per molecule -as exemplified by U.S. patent application Ser. No. 172,226 filed Aug.16, 1971 now U.S. Pat. No. 3,758,635; (l) a self-crosslinkable,epoxy-functional, anhydride-functional copolymer of olefinicallyunsaturatd monomers - exemplified by U.S. patent application Ser. No.172,235 filed Aug. 16, 1971, now U.S. Pat. No. 3,758,632; (m) anepoxy-functional copolymer of monovinyl monomers and as crosslinkingagent therefor a carboxy terminated polymer, e.g., a carboxy terminatedpolymer, e.g., a carboxy terminated polyester - exemplified byapplication Ser. No. 223,746 filed Feb. 4, 1972; and abandoned in favorof continuation-in-part application Ser. No. 489,271 filed Aug. 5, 1974.(n) an epoxy-functional copolymer of vinyl monomers and as crosslinkingagent therefor a dicarboxylic acid -- exemplified by U.S. patentapplication Ser. No. 228,262 filed Feb. 22, 1972, now U.S. Pat. No.3,787,521; (o) an epoxy-functional and hydroxy-functional copolymer ofmonovinyl monomers and as crosslinking agent therefor a C₄ -C₂₀,saturated, straight chain, aliphatic dicarboxylic acid -- exemplified byU.S. patent application Ser. No. 394,874 filed Sept. 6, 1973; and nowabandoned in favor of continuation-in-part application Ser. No. 552,676filed Feb. 24, 1975 (p) an epoxy-functional copolymer of monovinylmonomers with optional hydroxy and/or amide functionality and ascrosslinking agent therefore (1) a C₄ -C₂₀, saturated, straight chain,aliphatic dicarboxylic acid and (2) a polyanhydride-exemplified by U.S.patent application Ser. No. 344,881 filed Sept. 6, 1973; and nowabandoned in favor of continuation-in-part application Ser. No. 552,556filed Feb. 24, 1975 and continuation-in-part application Ser. No.552,557 filed Feb. 24, 1975 (q) an epoxy-functional, amide-functionalcopolymer of monovinyl monomers and as crosslinking agent therefor ananhydride of a dicarboxylic acid - exemplified by U.S. patentapplication Ser. No. 394,880 filed Sept. 6, 1973; and now abandoned infavor of continuation-in-part application Ser. No. 552,572 filed Feb.24, 1975 (r) an epoxy-functional, hydroxy-functional copolymer ofmonovinyl monomers and as crosslinking agent therefore an anhydride of adicarboxylic acid - exemplified by U.S. patent application Ser. No.394,879 filed Sept. 6, 1973; and now abandoned in favor ofcontinuation-in-part application Ser. No. 552,511 filed Feb. 24, 1975(s) an epoxy-functional, amide-functional copolymer of monovinylmonomers and as crosslinking agent therefore a carboxy-terminatedpolymer -- exemplified by U.S. patent application Ser. No. 394,875 filedSept. 6, 1973; and now abandoned in favor of continuation-in-partapplication Ser. No. 552,518 filed Feb. 24, 1975 (t) an epoxy-functionalcopolymer of monovinyl monomers and as crosslinking agent therefore amonomeric or polymeric anhydride and a hydroxy carboxylic acid --exemplified by U.S. patent application Ser. No. 394,878 filed Sept. 6,1973; and now abandoned in favor of continuation-in-part applicationSer. No. 552,079 filed Feb. 24, 1975 (u) an epoxy-functional,amide-functional copolymer of monovinyl monomers and as crosslinkingagent therefore a monomeric or polymeric anhydride and a hydroxycarboxylic acid -- exemplified by U.S. patent application Ser. No.394,877 filed Sept. 6, 1973; and now abandoned in favor ofcontinuation-in-part application Ser. No. 552,078 filed Feb. 24, 1975and (v) an epoxy-functional, hydroxy functional copolymer of monovinylmonomers and as crosslinking agent therefore a monomeric or polymericanhydride and a hydroxy carboxylic acid -- exemplified in U.S. patentapplication Ser. No. 394,876 filed Sept. 6. 1973 and now abandoned infavor of continuation-in-part application Ser. No. 552,077 filed Feb.24, 1975.

Other thermoset film-formers suitable for use in coating the metalparticles include, but not by way of limitation thermosettable systemsin which the polymeric component is a polyester, a polyepoxide andurethane-modified polyesters, polyepoxides and acrylices. As with theacrylics heretofore more specifically described, these may beself-crosslinking polymers or may be a combination of functional polymerand a coreactable monomeric compound which serves as crosslinking agent.

The preferred thermosettable powder paints known to applicants forautomotive topcoats, the use wherein metallic pigments find theirgreatest use, consist essentially of an epoxy functional copolymer ofolefinically unsaturated monomers and a crosslinking agent therefor.Such paints, excluusive of pigments, may also contain flow controlagents, catalysts, etc. in very small quantities.

The copolymer referred to in the preceding paragraph has averagemolecular weight (M_(n)) in the range of about 1500 to about 15,000 andglass transition temperature in the range of about 40°C. to about 90°C.The epoxy functionality is provided by employing a glycidyl ester of amonoethylenically unsaturated carboxylic acid, e.g., glycidyl acrylateor glycidyl methacrylate, as a constituent monomer of the copolymer.This monomer should comprise about 5 to about 20 weight percent of thetotal. Additional functionality, e.g., hydroxy functionality or amidefunctionality, may also be employed by inclusion of a C₅ -C₇ hydroxyacrylate or methacrylate, e.g., hydroxyethyl acrylate, hydroxyethylmethacrylate, hydroxypropyl acrylate, or hydroxypropyl methacrylate, oran alpha-beta olefinically unsaturated amide, e.g., acrylamide ormethacrylamide, among the constitutent monomers. When such additionalfunctionality is used, the monomers providing it comprise about 2 toabout 10 weight percent of the constituent monomers. The balance of thecopolymer, i.e., about 70 to about 93 weight percent of the constituentmonomers, are made up of monofunctional, olefinically unsaturatedmonomers, i.e., the sole functionality being ethylenic unsaturation.These monofunctional, olefinically unsaturated monomers are, at least inmajor proportion, i.e., in excess of 50 weight percent of theconstituent monomers, acrylic monomers. The preferred monofunctionalacrylic monomers for this purpose are esters of C₁ -C₈ monohydricalcohols and acrylic or methacrylic acid, e.g., methyl methacrylate,ethyl acrylate, propyl methacrylate, butyl acrylate, butyl methacrylate,hexyl acrylate and 2-ethylhexyl acrylate. In this preferred embodiment,the remainder, if any, aside from the aforementioned epoxy, hydroxy andamide functional monomers which also have olefinic unsaturationfunctionality used up in the polymerization formation of the copolymer,is preferably made up to C₈ -C₁₂ monovinyl hydrocarbons, e.g., styrene,vinyl toluene, alpha methyl styrene and tertiary butyl styrene. Othervinyl monomers which are suitable in minor amounts, i.e., between 0 and30 weight percent of the constituent monomers, include vinyl chloride,acrylonitrile, methacrylonitrile, and vinyl acetate.

The crosslinking agents employed with the aforedescribed copolymer willhave functionality that will react with the functionality of thecopolymer. Thus, all of the crosslinking agents heretofore mentioned inthe recital of powder paint patents and patent applications, e.g., C₄-C₂₀ saturated, aliphatic dicarboxylic acids, mixtures of C₄ -C₂₀saturated aliphatic dicarboxylic acids and monocarboxylic acids ofcarbon number in the same range, carboxy terminated copolymers havingmolecular weight (M_(n)) in the range of 650 to 3000, monomericanhydrides preferably anhydrides having a melting point in the range ofabout 35° to 140°C., e.g., phthalic anhydride, maleic anhydride,cyclohexane-1,2-dicarboxylic anhydride, succinic anhydride, etc.,homopolymers of monomeric anhydrides, and mixtures of such anhydridesand hydroxy acids having a melting point in the range 40° to 150°C., aresuitable for use as crosslinking agents for these copolymers. Thedisclosures of all patents and patent applications recited herein areincorporated herein by reference. In general, these crosslinking agentsare employed in amounts such as to provide between about 0.3 and about1.5, preferably between about 0.8 and about 1.2, functional groups whichare reactable with functional groups on the copolymer per functionalgroup on the copolymer.

The best acrylic, thermoplastic, powder coatings known to applicants arecopolymers of alpha-beta olefinically unsaturated monomers. These aremade up either solely or predominantly of acrylic monomers, i.e.,acrylates, methacrylates, mixtures of acrylates and methacrylates and asmall fraction of acrylic or methacrylic acid. In the embodiment whereinthe copolymer is made up predominantly of acrylic monomers, the acrylicmonomers may include up to about 5 weight percent acrylic acid,methacrylic acid or a mixture of acrylic and metacrylic acids whilei.e., in excess of 51 weight percent acrylic monomers, the balance ismade up of C₈ -C₁₂ monovinyl hydrocarbons, e.g., styrene, vinyl toluene,alpha methyl styrene, and tertiary butyl styrene. The acrylates andmethacrylates used in either of these embodiments are preferably estersof a C₁ -C₈ monohydric alcohol and acrylic acid or methacrylic acid or amixture of acrylic and methacrylic acids.

Thus, such a copolymer could contain about 46 to about 100 weightpercent of esters of a C₁ -C₈ monohydric alcohol and acrylic ormethacrylic acid, 0 to 49 weight percent of C₈ -C₁₂ monovinylhydrocarbons, and 0 to about 5 weight percent acrylic or methacrylicacid with the sum of the aforementioned esters and acrylic ormethacrylic acid comprising in excess of 5 weight percent of thecomonomers as stated earlier in this paragraph. One such copolymercontains about 76 to about 81 mole percent methyl methacrylate 1 to 3mole percent acrylic acid or methacrylic acid or a mixture of acrylicand methacrylic acids, and 16 to 23 mole percent butyl methacrylate.

The term "vinyl monomer" as used herein means a monomeric compoundhaving in its molecular structure the functional group ##EQU1## whereinX is a hydrogen atom or a methyl group.

The term "copolymer" as used herein means a polymer formed from two ormore different monomers.

"Alpha-beta unsaturation" as used herein includes both the olefinicunsaturation that is between two carbon atoms which are in the alpha andbeta positions relative to an activating group such as a carboxyl group,e.g., the olefinic unsaturation of maleic anhydride, and the olefinicunsaturation between the two carbon atoms which are in the alpha andbeta positions with respect to the terminus of an aliphaticcarbon-to-carbon chain, e.g., the olefinic unsaturation of acrylic acidor styrene.

DETAILED DESCRIPTION OF THE INVENTION

The preparation of the coated metal flakes is carried out in a solventfor the film-former that is sufficiently volatile for efficient spraydrying and which will not chemically react with either the film-formeror the metal flakes to a degree that will significantly modify theirproperties or appearance within the contact times employed to carry outthe spray drying process. A preferred solvent for this purpose ismethylene chloride. Other solvents which can be used include toluene,xylene, methyl ethyl ketone, acetone and low boiling petroleum naphthas.

A typical formulation for a feed stock for the spray drier in accordancewith this invention would include the following:

                     Parts By Weight                                              ______________________________________                                        aluminum paste     30.00                                                      film former        2.00                                                       MeCl.sub.2         200.00                                                     ______________________________________                                    

Typical operating parameters for a conventional, 3 ft. diameter spraydrier equipped with a conventional two-fluid nozzle atomizer, e.g., agas and a liquid as in a conventional air atomizing (liquid) paint spraygun, are as follows:

    air flor         197 cubic feet/minute                                        feed flow        380 ml/min.                                                  inlet air temperature                                                                          180°F.                                                outlet air temperature                                                                          80°F.                                                product rate     6 lbs./hr.                                               

The coated aluminum, as received from the spray drier, is then sievedthrough a screen of desired particulate size, e.g., a 44 micron screen,to remove excessively large particles. Approximately 20% of the productin the form of oversize particles is discarded.

The non-metal powder component, hereinafter called the "powdercomponent" comprises the primary film-forming component and, where thefinish is to be polychromatic, at least one non-metal color producingcomponent. This non-metal color producing component may be a pigment,dye or tint. For purposes of this invention, white and black shall beconsidered colors inasmuch as a light reflecting or light absorbingmaterial must be added to the organic film-former to provide the finishwith a white or black appearance in the same manner that a material mustbe added to the organic film-former which reflects light rays thatconvey to the eye one color while absorbing others.

The film-forming component of the powder component is preferably athermosetting film-forming material. Those thermosetting film-formingmaterials heretofore disclosed for use in coating the metal leaves aresuitable for use as the principal film-former of the powder component.The thermosets preferred for the coating of the metal leaves are alsothe preferred thermosets for this purpose.

In addition, the principal film-former of the powder component of thisinvention may be a thermoplastic powder, e.g., a thermoplastic, acrylicpolymer having a molecular weight (M_(n)) in the range of 30,000 to80,000 and a glass transition temperature in the range of 60°C. to110°C. -- as exemplified by U.S. patent application Ser. No. 172,227filed Aug. 16, 1971. A variety of other thermoplastic powders which canbe used with the encapsulated aluminum flakes and nickel powder aredisclosed in U.S. Pat. No. 3,532,530 which is incorporated herein byreference. These coated flakes, of course, can be used with anythermoplastic powder suitable for use as the principal film-former ofany thermoplastic powder paint.

The formulation of the non-metal powder component, which in the case ofa polychromatic finish contains a non-metal color producing component,is prepared taking into consideration the particular color chosen foremployment with the metallic color component and the amount of themetallic color component to be employed. The powder component isquantitatively formulated taking into account the amount of material tobe brought in through the addition of the metal color producingcomponent, i.e., the combination or sum of the encapsulated aluminumflakes and the nickel powder.

A typical composition for the powder component is as follows:

                    Parts by Weight                                               ______________________________________                                        film-former       94.33                                                       flow control additive                                                                           0.67                                                        pigment (non-metal)                                                                             5.00                                                        ______________________________________                                    

The preparation and processing of the non-metal powder component intopowder form is carried out by one of the conventional powder preparationtechniques, e.g., extrusion, spray drying, or solvent extraction. Oncein powdered form, this material is sieved through a suitable screen,e.g., a 74 micron screen.

The final step in the preparation of the powder coating material of thisinvention is the blending of the two major components, i.e., the metalcomponent consisting of encapsulated aluminum flake and nickel powderand the non-metal powder component. The exact proportions of the twomajor components will, of course, depend on the specific formulation andthe amount of metal needed. In the typical example aforedescribed, ifone blends about 98.5 parts by weight of the non-metal powder componentwith about 1.5 parts by weight of the metal component, a "low metallic"automotive top coat paint results.

Appearance of the finished coating will, of course, be a primary factorin selecting the total concentration of metal in the total powder paintcomposition. This concentration will vary from a very low weight percentof the total powder paint composition in some polychromatic finishes,i.e., as low as about 0.005 weight percent, to a much higher weightpercent of the total powder paint composition in the so called "Argent"finishes, i.e., as high as about 25 weight percent when aluminum is theonly metal used. If for example, the spray dried coating on the flakescomprises about 2 to about 30 weight percent by weight of the flakesthen, the total metal component of the powder paint composition willcomprise between about 0.005 to about 32.50, advantageously betweenabout 0.25 to about 28.75, and preferably between about 0.54 to about28.25, weight percent of the total powder paint composition. Thesefigures will be modified by the weight of nickel powder substituted fora portion of the aluminum. The principal film-forming powder andnon-metal pigment, if any, will make up the balance of the powder paintcomposition. The non-metal pigment will constitute between 0 and about22 weight percent of the total composition.

This invention will be more fully understood from the followingillustrative examples.

EXAMPLE 1 a Preparation of the Coated Aluminum Flakes

A powder paint in accordance with this invention is prepared from thefollowing materials using the procedures hereinafter outlined:

1. Preparation of an epoxy-functional acrylic copolymer of alpha-betaolefinically unsaturated monomers is prepared as follows:

    Ingredients       Parts By Weight                                             ______________________________________                                        glycidyl methacrylate                                                                           15                                                          methyl methacrylate                                                                             45                                                          butyl methacrylate                                                                              40                                                          ______________________________________                                    

The above named ingredients are mixed together. Three (3) parts byweight of 2,2'-azobis-(2-methyl-propionitrile), hereinafter called AIBN,is dissolved in the monomer mixture. The mixture is slowly added torefluxing toluene (100 parts) which is stirred vigorously under anitrogen atmosphere. A condenser is provided at the top of the toluenecontainer to condense the toluene vapors and return them to thecontainer. The monomer mixture is added through a regulating valve andthe rate of addition is controlled to maintain a reflux temperature(109°C.-112°C.) with only a small fraction of heat supplied from anexternal heater. After the addition of the monomer mixture is complete,the refluxing is maintained by external heat source for 3 additionalhours.

The solution is poured into shallow stainless steel trays. These traysare placed in a vacuum oven and the solvent evaporated therefrom. As thesolvent is removed, the copolymer solution becomes more concentrated.The temperature of the vacuum oven is raised to about 110°C. Drying iscontinued until the solvent content of the copolymer is below 3 percent.The trays are cooled and the copolymer collected and ground to passthrough 20 mesh screen. The copolymer has a glass transition temperatureof 53°C. and a molecular weight (M_(n)) of 4000.

One hundred parts by weight of the ground copolymer are mixed with thefollowing materials:

                        Parts By Weight                                           ______________________________________                                        azelaic acid          10.0                                                    poly (lauryl acrylate)(M.sub.n =10,000                                                              0.7                                                     ______________________________________                                    

The materials are mixed together in a ball mill for 2 hours. The mixtureis mill rolled at 85°C. to 90°C. for 5 minutes. The solid obtained isground in a ball mill and the powder is sieved with a 140 mesh screen.

Two parts by weight of this thermosettable mixture are combined with 30parts by weight of aluminum paste (35% by weight mineral spirits and 65%by weight aluminum flakes that will pass through a 325 mesh screen andhave typical surface area of 7.5 m² /g, maximum particle diameter below45 microns and most common particle size distribution in the range ofabout 7 to about 15 microns) and 200 parts by weight of methylenechloride under low shear agitation so as to disperse the aluminum in thethermosettable material without damage to the aluminum flakes.

Once the above dispersion has been prepared, it is spray dried in amanner which will produce individual aluminum flakes coated with a thin,continuous coating of dry copolymer. This is accomplished in a 3 footdiameter spray drier equipped with a two-fluid nozzle in counter-currentposition using the following conditions:

    air flow in drying chamber                                                                      200 cubic feet/minute                                       feed rate of mixture                                                                            380 ml/minute                                               inlet air temperature                                                                           180°F.                                               two fluid atomization air pressure 80 lbs.                                

The product obtained from this process has an overall composition of19.5 parts by weight of aluminum and 2.0 parts by weight of thethermosettable mixture aforedescribed plus a small amount of residualsolvent (i.e., 0.05 to 0.2 parts) that has not completely volatilizedduring the spray dry process. This product is then screened through a 44micron screen.

b. Preparation of the Non-Metal Powder Component

A thermosettable material is produced by mixing 166 parts by weight ofthe epoxy-functional copolymer employed in the thermosettable materialused to coat the aluminum flakes in (a) above with the followingmaterials:

                     Parts By Weight                                              ______________________________________                                        azelaic acid       22.65                                                      poly (lauryl acrylate)                                                                           1.34                                                       phthalo green pigment                                                                            1.75                                                       yellow iron oxide pigment                                                                        8.26                                                       ______________________________________                                    

A homogeneous mixture of the above is obtained by ball milling for 2hours. This mixture is then extruded at 100°C. from a kneading extruder.The solid thus obtained is pulverized in an impact mill, i.e., an airclassified impact mill, and sieved through a 200 mesh screen.

c. Preparation of the Powder Coating Material

A powder coating material in accordance with this invention is producedby blending 98.5 parts by weight of the non-metal powder component from(b) with the following materials:

                       Parts By Weight                                            ______________________________________                                        nickel powder (325 mesh)                                                                           1.0                                                      coated aluminum flakes from (a)                                                                    .55                                                      ______________________________________                                    

The resultant powder coating composition on a solids basis is asfollows:

                        Parts By Weight                                           ______________________________________                                        nickel powder (flakes)                                                                              1.00                                                    aluminum flake (uncoated basis)                                                                     .50                                                     epoxy-functional copolymer from (a)                                                                 81.77                                                   poly (lauryl acrylate) -M.sub.n =10,000                                                             .66                                                     phthalo green         .86                                                     yellow iron oxide     4.05                                                    azelaic acid          11.15                                                   ______________________________________                                    

It will be noted that in this example the thermosettable material usedto coat the aluminum flakes and the thermosettable material used to formthe non-metal powder component are crosslinkable with each other.

The powder thus obtained is then sprayed on an electrically groundedsteel substrate with a conventional electrostatic powder spray gunoperating at about 50 KV charging voltage. After spraying, the coatedsubstrate is heated to about 350°F. for about 25 minutes. The coatingthus obtained has good appearance and physical properties. The coatingthus obtained demonstrates a more random metal particle orientation withrespect to depth and increased polychromatic light reflection of thecured film than is obtained when this process is duplicated except forsubstituting an equal volume of aluminum flakes of like size for thenickel powder.

EXAMPLE 2

The procedure of Example 1 is repeated except for the difference thatthe weight ratio of nickel powder to coated aluminum flake is 1:4. Thecoating thus obtained has good appearance, good physical properties, anda random metal particle orientation with respect to depth. With thechange in ratio, there is, of course, a change in polychromaticappearance. This flexibility is advantageous in preparing a variety ofmarket-acceptable, polychromatic coatings with the same or differentnon-metal pigments.

EXAMPLE 3

The procedure of Example 1 is repeated except for the difference thatthe weight ratio of nickel powder to coated aluminum flake is 5:1. Thecoating thus obtained has good appearance, good physical properties, anda random metal particle orientation with respect to depth. Thisflexibility is advantageous in preparing a variety of market-acceptable,polychromatic coatings with the same or different non-metal pigments.

EXAMPLE 4

The procedure of Example 1 is repeated except for the difference thatthe weight ratio of nickel powder to coated aluminum flake is 1.5:1. Ancoating of outstanding appearance is obtained and the physicalproperties of the film are good.

EXAMPLE 5

The procedure of Example 1 is repeated except for the the differencethat the weight ratio of nickel powder to coated aluminum flake is2.5:1. A coating of outstanding appearance is obtained and the physicalproperties of the film are good.

EXAMPLE 6

A powder coating material is prepared following the procedure of Example1 with the following differences: (1) the coated aluminum flakes areprepared from the following materials:

                        Parts By Weight                                           ______________________________________                                        aluminum paste        30.000                                                   (65% aluminum flakes                                                          and 35% mineral spirits)                                                     thermosettable mixture                                                                              0.218                                                    (same epoxy-functional co-                                                    polymer used in Example 1                                                     in amount as 0.195 parts by                                                   weight and poly (azelaic an-                                                  hydride) 0.023 parts by weight                                               poly (lauryl acrylate)M.sub.n =10,000                                                               0.001                                                   methylene chloride    197.000                                                 ______________________________________                                    

The product obtained after spray drying has a composition of 19.50 partsby weight aluminum, 0.218 parts by weight thermosettable material and0.001 parts by weight poly (lauryl acrylate).

The coated aluminum thus produced in the amount of 0.52 parts by weightand 1.0 parts by weight of 325 mesh nickel powder are combined with98.48 parts by weight of the non-metal powder component of Example 1 toyeild a powder coating composition.

This powder coating material is electrodeposited upon a metal substrateand heat cured as in Example 1. The resulting coating demonstrates goodgloss, good orientation of the aluminum flakes, good depth variation ofthe metal particles, and weathering resistance.

EXAMPLE 7

A powder coating material is prepared following the procedure of Example1 with the following differences: (1) The starting mixture forpreparation of the coated aluminum flakes is of the followingcomposition:

                       Parts By Weight                                            ______________________________________                                        aluminum paste       30.00                                                    (65% by wt. aluminum and 35%                                                  by weight mineral spirits)                                                    thermosettable mixture                                                                             5.46                                                      (a) epoxy-functional copolymer                                                 of Example 1 - 4.88                                                          (b) poly (azelaic                                                              anhydride) - 0.58                                                           poly (lauryl acrylate)                                                                             0.03                                                     methylene chloride   250.00                                                   ______________________________________                                    

This material is mixed and spray dried as in Example 1 and in theresultant material the flakes have coating about 2.5 times thicker thanthat of the coated flakes of Example 1. The empirical composition of thespray dried product by weight is as follows:

                        Parts By Weight                                           ______________________________________                                        aluminum (uncoated basis                                                                            19.50                                                   thermosettable material                                                                             5.46                                                     (a) epoxy copolymer of                                                          Example 1 - 4.88                                                            (b) poly (azelaic anhydride)-0.58                                            poly (lauryl acrylate)                                                                              0.03                                                    ______________________________________                                    

(2) Since the amount of coating on the aluminum flakes is here largeenough to be a significant factor, it is taken into consideration whenformulating the non-metal powder component to maintain the same relativequantities of pigment and film-former. (3) The weight ratio of thenickel powder to coated aluminum flakes is 2.1:1.

EXAMPLE 8

The procedure of Example 1 is repeated except for the differences:

1. the coating of the aluminum flakes is prepared from 30 parts byweight of the same aluminum paste used in Example 1 (19.5 parts byweight aluminum), and 4.7 parts by weight of the thermosettablematerial, i.e., epoxy-functional copolymer of Example 1 and azelaic acidin the porportions used in Example 1 and 0.03 parts by weight poly(lauryl acrylate), and

2. Following the procedure of Example 7, the non-metal powder componentis adjusted and employed in an amount to provide the powder coatingmaterial to be sprayed with the same level of pigment loading as in suchmaterial in Example 1, and

3. the weight ratio of nickel powder to coated aluminum flakes is 1.8:1.

The cured finish obtained has good physical properties and good depthvariation in metal pigment positioning.

EXAMPLE 9

The procedure of Example 1 is repeated except for the differences:

1. the coating of the aluminum flakes is prepared from 30 parts byweight of aluminum paste used in Example 1 (19.5 parts by weightaluminum) and from 2.93 parts by weight of the thermosettable material,i.e., epoxy-functional copolymer of Example 1 and azelaic acid in theproportions used in Example 1, and 0.02 parts by weight poly (laurylacrylate) and

2. Following the procedure of Example 7, the nonmetal powder componentis adjusted and employed in an amount to provide the powder coatingmaterial to be sprayed with the same level of pigment loading as in suchmaterial in Example 1, and

3. the weight ratio of nickel powder to coated aluminum flakes is 1:2.

The cured finish obtained has good physical properties and good depthvariation in metal pigment positioning.

EXAMPLE 10

The procedure of Example 1 is repeated except for the followingdifferences:

1. The coating of the aluminum flakes is prepared from 30 parts byweight of the aluminum paste used in Example 1 (19.5 parts by weightaluminum) and 1.76 parts by weight of the thermosettable material, i.e.,the epoxy-functional copolymer of Example 1 and azelaic acid in theproportions used in Example 1, and 0.01 parts by weight poly (laurylacrylate) - M_(n) = 10,000, and

2. the weight ratio of nickel powder to coated aluminum flakes is 1:1.

The cured finish obtained has good physical properties and good depthvariation in metal pigment positioning.

EXAMPLE 11

The procedure of Example 1 is repeated except for the followingdifferences:

1. The coating of the aluminum flakes is prepared from 30 parts byweight of the aluminum paste used in Example 1 (19.5 parts by weightaluminum) and 2.54 parts by weight of the thermosettable material, i.e.,the epoxy-functional copolymer of Example 1 and azelaic acid in theproportions used in Example 1, and 0.01 parts by weight poly (laurylacrylate) -M_(n) = 10,000, and

2. Following the procedure of Example 7, the non-metal powder componentis adjusted and employed in an amount to provide the powder coatingmaterial to be sprayed with the same level of pigment loading as in suchmaterial in Example 1, and

3. the weight ratio of nickel powder to coated aluminum flakes is 1:3.

The cured finish obtained has good physical properties and good depthvariation in metal pigment positioning.

EXAMPLE 12

The procedure of Example 1 is repeated except for the followingdifferences:

1. The coating of the aluminum flakes is prepared from 30 parts byweight of the aluminum paste used in Example 1 (19.5 parts by weightaluminum) and 0.39 parts by weight of the thermosettable material, i.e.,epoxy-functional copolymer of Example 1 and azelaic acid in theproportions used in Example 1, and 0.002 parts by weight poly (laurylacrylate) -M_(n) = 10,000, and (2) the weight ratio of nickel powder tocoated aluminum flakes is 1:2.

The cured finish obtained has good physical properties and good depthvariation in metal pigment positioning.

EXAMPLE 13

The procedure of Example 1 is repeated except for the difference that afunctionally equivalent amount of an epoxyfunctional andhydroxy-functional copolymer of alpha-beta olefinically unsaturatedmonomers is substituted for the epoxyfunctional copolymer of Example 1and a functionally equivalent amount of poly (azelaic anhydride) issubstituted for the azelaic acid. The epoxy-functional andhydroxy-functional copolymer used in this example is prepared from thebelow listed components in the manner hereinafter described:

                             Percent By Weight                                    Reactants      Grams     Of Total Reactants                                   ______________________________________                                        glycidyl methacrylate                                                                        225.0     15                                                   hydroxyethyl methacry-                                                        late           75.0      5                                                    butyl methacrylate                                                                           600.0     40                                                   styrene        75.0      5                                                    methyl methacrylate                                                                          525.0     35                                                   ______________________________________                                    

The above mentioned monomers are admixed in the proportions above setforth and 70.0 grams (4.5% based on combined weights of reactants) of2,2'-azobis-(2-methyl propionitrile), hereinafter called AIBN, are addedto the monomer mixture. The solution is added dropwise over a 3 hourperiod into 1500 ml. toluene at 100°-108°C. under nitrogen atmosphere.Then 0.4 grams of AIBN dissolved in 10 ml. of acetone are added over a1/2 hour period and refluxing is continued for 2 additional hours.

The toluene-polymer solution is diluted in 1500 ml. acetone andcoagulated in 16 liters of hexane. The white powder is dried in a vacuumoven at 55°C. for 24 hours. This copolymer has molecular weight - M_(w)-M_(n) = 6750/3400 and the molecular weight per epoxy group is about1068.

The cured finish obtained from the powder coating composition utilizingthe above film-former demonstrates good physical properties, good metalparticle orientation and good depth variation of the metal particles.

EXAMPLE 14

The procedure of Example 13 is repeated with the single difference thatabout 35% of the poly (azelaic anhydride) is replaced with afunctionally equivalent amount of 12-hydroxystearic acid.

EXAMPLE 15

The procedure of Example 1 is repeated except for the difference that anepoxy-functional, amide-functional copolymer of alpha-beta olefinicallyunsaturated monomers is substituted for the epoxy-functional copolymerof Example 1 and a functionally equivalent amount of acarboxy-terminated polymer is substituted for the azelaic acid. Theepoxy-functional, amidefunctional copolymer used in this example isprepared from the below listed components in the manner hereinafterdescribed:

                              Percent By Weight                                   Reactants      Grams      Of Total Reactants                                  ______________________________________                                        glycidyl methacrylate                                                                        45         15                                                  acrylamide     15         5                                                   butyl methacrylate                                                                           111        37                                                  methyl methacrylate                                                                          129        43                                                  ______________________________________                                    

The above mentioned monomers are admixed in the proportions above setforth and 11.0 grams of 2,2'-azobis-(2-methylpropionitrile), hereinaftercalled AIBN, are added to the mixture. The mixture is slowly added to200 ml. of toluene heated to 80°-90°C. which is being stirred vigorouslyunder a nitrogen atmosphere. A condenser is provided at the top of thetoluene container to condense the toluene vapors and return thecondensed toluene to the container. The monomer mixture is added througha regulating valve and the rate of addition is controlled to maintain areaction temperature of 90°-110°C. with the rest of the heat suppliedfrom an external heater. After the addition of the monomer mixture iscompleted (3hours), 0.8 gram of AIBN dissolved in 10 ml. acetone isadded over a one-half hour period and refluxing is continued for twoadditional hours.

The resultant toluene-polymer solution is diluted with 200 mls. acetoneand coagulated in 2 liters of hexane. The white powder is dried in thevacuum oven at 55°C. for 24 hours. Its molecular weight is determined tobe M_(w) /M_(n) = 6700/3200 and WPE (molecular weight per epoxide group)is about 1000.

The carboxy terminated polymer to be used as crosslinking agent isprepared from the following materials in the following manner: Fivehundred grams of a commercially available epoxy resin, Epon 1001,(epoxide equivalent 450-525, melting range 64°-76°C. - molecular weightaverage 900°C.), is charge into a 500 ml. stainless steel beaker havinga heating mantle. The epoxy resin is heated to 110°C. As the epoxy resinis stirred, 194 grams of azelaic acid are added. After a reaction timeof 30 minutes, a homogeneous mixture is obtained. The mixture resin,only semi-reacted, is poured out into an aluminum pan and cooled. Thesolid mixture is pulverized to pass through a 100 mesh screen by use ofa blender. This resin is only partially reacted because if fully reactedit could not be powdered. A portion of the carboxy terminated polymer isweighed out for making a powder coating composition in accordance withthis invention.

The cured finish obtained from the powder coating composition utilizingthe above film-former demonstrates good physical properties, good metalparticle orientation and good depth variation of the metal particles.

EXAMPLE 16

The procedure of Example 1 is repeated except for the difference that afunctionally equivalent amount of a hydroxy-functional copolymer issubstituted for the epoxyfunctional copolymer of Example 1 and afunctionally equivalent amount of hexamethoxy melamine is substitutedfor the azelaic acid.

The hydroxy-functional copolymer used in this example is prepared fromthe below listed components in the manner hereinafter described:

    Reactants           Parts By Weight                                           ______________________________________                                        2-hydroxyethyl methacrylate                                                                       15                                                        ethyl acrylate      25                                                        methyl methacrylate 60                                                        ______________________________________                                    

A 1 liter, four-necked flask which contains 150 ml. of methyl ethylketone is heated until the contents of the flask are at a refluxingtemperature of 85°C. A mixture of the above listed monomers and 4 partsby weight of 2,2' -azobis-(2-methyl propionitrile), hereinafter calledAIBN, in the total amount of 208 grams is added in a dropwise fashionover a period of one and a half hours to the reaction mixture which ismaintained at 85°C. After the monomer addition is complete, 0.5 grams ofAIBN (dissolved in 20 grams of toluene) is added dropwise. The refluxingis continued for an additional one-half hour to complete thepolymerization.

The solution is poured into shallow stainless steel trays. These traysare placed in a vacuum oven and the solvent evaporated therefrom. As thesolvent is removed, the copolymer becomes more concentrated. Thetemperature of the vacuum oven is raised to 110°C. Drying is continueduntil the solvent content of the copolymer is below 3 percent. The traysare cooled and the copolymer collected and ground to pass through a 20mesh screen.

The cured finish obtained from the powder coating composition utilizingthe above film-former demonstrates good physical properties, good metalparticle orientation and good depth variation of the metal particles.

EXAMPLE 17

The procedure of Example 1 is repeated except for the difference that afunctionally equivalent amount of a self-crosslinking copolymer issubstituted for the epoxy-functional copolymer and the azelaic acid.

The self-crosslinking copolymer used in this example is prepared fromthe following listed components in the manner hereinafter described:

    Reactants        Grams                                                        ______________________________________                                        glycidyl methacrylate                                                                          30                                                           methacrylic acid 21                                                           methyl methacrylate                                                                            129                                                          butyl methacrylate                                                                             120                                                          ______________________________________                                    

The monomers above listed are mixed with 12 grams of an initiator, i.e.,t-butylperoxypivate. Three hundred grams of benzene is charged into aone liter flask which is equipped with a dropping funnel, condenser,stirrer, thermometer and nitrogen inlet. The monomer mixture is placedin the dropping funnel. The flask is heated to 80°C. and a refluxing ofthe solvent is achieved. While maintaining the reaction temperature at80°C., the monomer mixture is added in a dropwise fashion over a twohour period. After the addition is complete, the reaction is continuedfor another two hours. The contents of the flask are then cooled to roomtemperature.

One hundred millileters of the resultant solution are mixed with 0.3grams of poly (2-ethylhexyl acrylate). The mixture is dispersed and thenis dried in a vacuum oven at 70°C. The powder coating obtained is groundto pass through a 200 mesh sieve.

The cured finish obtained from the powder coating composition utilizingthe above film-former demonstrates good physical properties, good metalparticle orientation and good depth variation of the metal particles.

EXAMPLE 18

The procedure of Example 1 is repeated except for the difference thatthe poly (lauryl acrylate) is replaced with an equivalent amount of poly(butyl acrylate) - M_(n) = 9000.

EXAMPLE 19

The procedure of Example 1 is repeated except for the difference thatthe poly (lauryl acrylate) is replaced with an equivalent amount of poly(isododecyl methacrylate).

EXAMPLE 20

The procedure of Example 1 is repeated except for the difference thatthe poly (lauryl acrylate) is replaced with an equivalent amount ofpolyethylene glycol perfluoro octonoate (M_(n) = 3400).

EXAMPLE 21

The procedure of Example 1 is repeated except for the difference thatthe coated aluminum flakes and the nickel powder are mixed with theprincipal film-forming powder in an amount such as to provide a metalpigment component which comprises 0.1 weight % of the total powder paintcomposition and the weight ratio of nickel powder to coated aluminumflakes is 1.75:1.

EXAMPLE 22

The procedure of Example 1 is repeated except for the difference thatthe coated aluminum flakes and the nickel powder are mixed with theprincipal film-forming powder in an amount such as to provide a metalpigment component which comprises 32.50 weight % of the total powderpaint composition and the weight ratio of nickel powder to coatedaluminum flakes is 2.25:1.

EXAMPLE 23

The procedure of Example 1 is repeated except for the difference thatthe coated aluminum flakes and the nickel powder are mixed with theprincipal film-forming powder in an amount such as to provide a metalpigment component which comprises 0.25 weight percent of the totalpowder paint composition and the weight ratio of nickel powder to coatedaluminum flakes is 1.5:1.

EXAMPLE 24

The procedure of Example 1 is repeated except for the difference thatthe coated aluminum flakes and the nickel powder are mixed with theprincipal film-forming powder in an amount such as to provide a metalpigment component which comprises 28.75 weight percent of the totalpowder paint composition and the weight ratio of nickel powder to coatedaluminum flakes is 2.5:1. In this example, non-metal pigments are notused.

EXAMPLE 25

The procedure of Example 1 is repeated except for the difference thatthe coated aluminum flakes and the nickel powder are mixed with theprincipal film-forming powder in an amount such as to provide a metalpigment component which comprises 0.45 weight percent of the totalpowder paint composition and the weight ratio of nickel powder to coatedaluminum flakes is 2:1.

EXAMPLE 26

The procedure of Example 1 is repeated except for the difference thatthe coated aluminum flakes and the nickel powder are mixed with theprincipal film-forming powder in an amount such as to provide a metalpigment component which comprises 10 weight percent of the total powderpaint composition and the weight ratio of nickel powder to coatedaluminum flakes is 2:1.

EXAMPLE 27

The procedure of Example 1 is repeated with the differences that thecoated aluminum flakes and the nickel powder are mixed with theprincipal film-forming powder in an amount such as to provide a metalpigment component which comprises weight percent of the total powderpaint composition and the weight ratio of nickel powder to coatedaluminum flakes is 2:1. In this example, the non-metal pigmentsconstitute 21.9 weight percent of the total powder paint composition.

EXAMPLE 28

The procedure of Example 1 is repeated with the following compositionaldifferences. The coated aluminum flakes and the nickel powder are mixedwith the principal film-forming in an amount such that they provide ametal pigment component which comprises 31.0 weight percent of the totalpaint composition, the weight ratio of nickel powder to coated aluminumflakes is 2:1 and the principal film-forming powder contains, as thesole non-metal pigment, phthalo green pigment in an amount such that itcomprises 0.25 weight percent of the total powder paint composition.

EXAMPLE 29

The procedure of Example 1 is repeated with the following compositionaldifferences. The coated aluminum flakes and the nickel powder are mixedwith the principal film-forming powder in an amount such that theycomprise 4.0 weight percent of the total powder with a weight ratio ofnickel powder to coated aluminum flakes of 2:1 and the principalfilm-forming powder contains a mixture of metal-free pigments in anamount such that it comprises 22 weight percent of the total powderpaint composition. The mixture of metal-free pigments consistspredominantly of chrome yellow with flaventhron (yellow organic), rediron oxide and carbon black present from trace amounts to above oneweight percent.

EXAMPLE 30

The procedure of Example 1 is repeated except for the difference thatthe principal film-forming material into which is mixed nickel powderand the encapsulated aluminum flakes is a thermoplastic powder coatingmaterial prepared from the following materials using the procedurehereinafter described.

    ______________________________________                                                          Parts By Weight                                             ______________________________________                                        poly (methyl methacrylate                                                                         100                                                          M.sub.n = 40,000                                                           poly (lauryl methacrylate)                                                                        2                                                            M.sub.n = 120,000                                                          tetrabutylammonium bromide                                                                        0.5                                                       ______________________________________                                    

Step I. The materials listed below are thoroughly mixed.

    __________________________________________________________________________                   A    B    C    D    E                                                         PARTS BY WEIGHT                                                __________________________________________________________________________    1.                                                                              aluminum paste                                                                (65% metal)  30.00                                                                              30.00                                                                              30.00                                                                              30.00                                                                              30.00                                      2.                                                                              thermosettable                                                                mixture      9.75 13.65                                                                              19.5 29.25                                                                              39.00                                        (a) resin*   8.58 12.01                                                                              17.16                                                                              25.74                                                                              34.32                                        (b) polyazelaic                                                                  anhydride 1.17 1.64 2.34 3.51 4.68                                            % based on                                                                    weight of alumi-                                                              num       50.00                                                                              70.00                                                                              100.00                                                                             150.00                                                                             200.00                                     3.                                                                              poly(lauryl acrylate)                                                                      0.06 0.08 0.12 0.18 0.23                                       4.                                                                              methylene chloride                                                                         250.00                                                                             250.00                                                                             250.00                                                                             250.00                                                                             250.00                                     __________________________________________________________________________     *epoxy-functional copolymer of Example 1.                                

Step II. This mixture is then spray dried as in the preceding examplesand a product comprising aluminum flakes encapsulated in athermosettable mixture of resin and cross-linking agent is obtainedwherein the relative weights of the components are as follows:

                   A    B    C    D    E                                                         PARTS BY WEIGHT                                                __________________________________________________________________________    1.  aluminum flakes                                                                          19.5 19.5 19.5 19.5 19.5                                       2. thermosettable mixture                                                                    9.75 13.65                                                                              19.50                                                                              29.25                                                                              39.00                                      3. poly(laurylacrylate)                                                                      0.06 0.08 0.12 0.18 0.23                                       __________________________________________________________________________

The above ingredients are mixed in a twin shell tumbling mixer for 10minutes and then mill rolled at 190°C. for 15 minutes. The blend iscooled and pulverized to pass through a 200 mesh screen.

The above materials in the amount of 188 parts by weight are mixed withthe yellow iron oxide pigment (8.26 parts by weight), phthalo greenpigment (1.75 parts by weight) and 1.34 parts by weight of poly (laurylacrylate).

A homogeneous mixture of the above is obtained by ball milling for 2hours. This mixture is extended at 100°C. from a kneading extruder. Thesolid thus obtained is pulverized in an impact mill, i.e., an airclassified impact mill, and sieved through a 200 mesh screen.

The finish coating obtained from the powder coating utilizing the abovefilm-former is a thermoplastic film with good metal particle orientationand depth variation.

EXAMPLE 31

The procedure of Example 1 is repeated with the following compositionaldifference: The coated aluminum flakes and the nickel powder are mixedwith the principal film-forming powder in an amount such that theycomprise 0.5 weight percent of the total powder paint composition andthe weight ratio of nickel powder to coated aluminum flades is 2:1.

EXAMPLE 32

A series of powder paints, A-E are prepared from the following materialsin the manner hereinafter set forth and later electrostatically sprayedas in Example 1 for test purposes.

Step III

These encapsulated aluminum flakes are sieved through a 44 micronscreen. All particles left on the screen are rejected.

Step IV

A non-metallic powder mixture is made up by thoroughly mixing the belowlisted materials after which the mixture is pulverized and sievedthrough a 75 micron screen. All particles left on the screen arerejected.

    __________________________________________________________________________                   A     B     C     D     E                                                     PARTS BY WEIGHT                                                __________________________________________________________________________    1. Resin*      166   166   166   166   166                                    2. Azelaic acid                                                                              22.64 22.64 22.64 22.64 22.64                                  3. Poly(lauryl                                                                  acrylate)    1.34  1.34  1.34  1.34  1.34                                   4. Pigments                                                                     (a) thalo green                                                                            2.03  2.03  2.04  2.06  2.08                                     (b) yellow iron oxide                                                                      8.04  8.07  8.11  8.18  8.25                                   __________________________________________________________________________     *epoxy-functional copolymer of Example 1                                 

Step V

An evenly mixed blend is formed from the encapsulated aluminum flakes ofStep III and the nonmetallic powder mixture of Step IV in the followingrelative proportions:

                 A    B    C    D    E                                                         PARTS BY WEIGHT                                                  __________________________________________________________________________    1. encapsulated aluminum                                                        flakes     2.255                                                                              2.556                                                                              3.009                                                                              3.764                                                                              4.518                                        2. nonmetallic powder                                                                      97.745                                                                             97.444                                                                             96.991                                                                             96.236                                                                             95.482                                       __________________________________________________________________________

The relative concentrations of ingredients in each of these blends is asfollows:

    Ingredient         Parts by Weight                                            ______________________________________                                        aluminum           1.50                                                       thermosettable material                                                        (resin and crosslinker)                                                                         92.91                                                      poly(laurylacrylate)                                                                             0.66                                                       phthalo green      0.99                                                       yellow iron oxide  3.93                                                       ______________________________________                                    

Each of the powders thus obtained are blended with nickel powder in anamount such that the weight ratio of nickel to aluminum is 2:1 and aresprayed on electrically grounded substrates and baked as in Example 1.Metal encapsulated pigmet spacing and orientation is best when the resinencapsulation on the aluminum flakes is in the range of 50 to 70 weightpercent of the aluminum with the very best achieved with paint A (50weight percent encapsulation based on the weight of aluminum flakes).

EXAMPLE 33

Aluminum flakes are encapsulated as in Example 1 except for thedifferences that solvents other than methylene chloride, i.e., toluene,xylene, acetone, hexane and methyl ethyl ketone, are used to dispersethe film-forming material and aluminum flakes prior to spray drying. Thespray srying operation is adjusted in conformance with the relativevolalities of the solvent are used in each test. The encapsulated flakesthus prepared are incorporated into the powder paint of Example 1,electrostatically sprayed upon substrates and the substrates are bakedas in Example 1.

Hydrocarbons, alcohols, and ketones boiling in the range of 50°C. to152°C., preferably 50°C. to 90°C., can be used for this purpose. Theamount of solvent used is in excess of the combined weights of thealuminum flakes and the film-former used for encapsulation.Advantageously, the amount of solvent used is in the range of about 3 to100 times the combined weights of film-former and aluminum flakes.

Apparatus and methods for electrostatically spraying powder coatingmaterials are illustrated and described in U.S. Pat. Nos. 3,536,514;3,595,678; and 3,598,629.

Many modifications of the foregoing examples will be apparent to thoseskilled in the art in view of this specification. It is intended thatall such modifications which fall within the scope of this invention beincluded within the appended claims.

The disclosures of U.S. patent application Ser. No. 442,291 filed Feb.12, 1974 by Santokh S. Labana et al and entitled "Powder CoatingCompositions Including Glycidyl Ester-Modified Copolymer" areincorporated herein by reference.

Any and all disclosures appearing in the claim and not specificallyappearing in the body of this specification are herewith incorporated inthe body of this specification.

We claim:
 1. In a powder paint which exclusive of catalysts, antistaticagents, plasticizers, and flow control agents, the same being known andoptional additives to powder paints, consists essentially of aluminumflakes, non-metal pigment, and a particulate, organic, film-former, theimprovement whereinA. said non-metal pigment comprises 0 to about 22weight percent of said powder paint, B. said aluminum flakes compriseabout 0.005 to about 25 weight percent of said powder paint and areencapsulated prior to admixture with said particulate, organic,film-former with about 2 to about 200 parts by weight of a continuouscoating of a thermosettable, organic, film-former per 100 parts byweight aluminum flakes, said thermosettable, organic, film-formerconsisting essentially of a copolymer having average molecular weight(M_(n)) in the range of about 1500 to about 15,000 and glass transitiontemperature in the range of about 40°C. to about 90°C. bearingfunctional groups provided by constituent monomers selected from thegroup consisting of glycidyl esters of a monoethylenically unsaturatedcarboxylic acid, C₅ -C₇ monohydroxy acrylates, C₅ -C₇ monohydroxymethacrylates and alpha-beta olefinically unsaturated amides and whereinat least above 50 weight percent of the constituent monomers areselected from acrylic monomers and the remainder weight percent, if any,of the constituent monomers consist essentially of C₈ -C₁₂ monovinylhydrocarbons, said copolymer being self-crosslinkable or employed incombination with a monomeric or polymeric crosslinking agent that iscapable of reacting with said functional groups on said copolymer. C.nickel powder is dispersed in said powder paint, the weight ratio ofsaid nickel powder to the encapsulated aluminum flakes being betweenabout 1:4 and about 5:1, and D. said particulate, organic film-former isselected from1. a thermoplastic, particulate, film-former that is apolymer of alpha-beta olefinically unsaturated monomers of which about51 to about 100 weight percent are acrylic monomers and 0 to about 49weight percent are monovinyl hydrocarbons, and
 2. thermosettable,particulate, film-formers consisting essentially of a copolymer havingaverage molecular weight (M_(n)) in the range of about 1500 to about15,000 and glass transition temperature in the range of about 40°C. toabout 90°C., bearing functional groups provided by constituent monomersselected from the group consisting of glycidyl esters of amonoethylenically unsaturated carboxylic acid, C₅ -C₇ monohydroxyacrylates, C₅ -C₇ monohydroxy methacrylates and alpha-beta olefinicallyunsaturated amides and wherein at least about 50 weight percent of theconstituent monomers are selected from acrylic monomers and theremainder weight percent, if any, of the constituent monomers consistessentially of C₈ -C₁₂ monovinyl hydrocarbons, said copolymer beingself-crosslinkable or employed in combination with a monomeric orpolymeric cross-linking agent that is capable of reactions with saidfunctional groups on said copolymer.
 2. A powder paint in accordancewith claim 1 wherein the weight ratio of said nickel powder to saidencapsulated aluminum flakes is between about 1.5:1 and about 2.5:1. 3.A powder paint in accordance with claim 1 wherein the encapsulation ofsaid aluminum flakes is in the amount of about 2 to about 30 parts byweight of thermosettable, organic, film-former per 100 parts by weightof said aluminum flakes.
 4. A powder paint in accordance with claim 1wherein the encapsulation of said aluminum flakes is in the amount ofabout 30 to about 70 parts by weight of thermosettable, organic,film-former per 100 parts by weight of said aluminum flakes.
 5. A powderpaint in accordance with claim 1 wherein said aluminum flakes areencapsulated in a thermosettable, organic film-former consistingessentially of a copolymer which is a copolymer of monoethylenicallyunsaturated monomers of which about 5 to about 20 weight percent areglycidyl esters of a monoethylenically unsaturated carboxylic acid, inexcess of 50 weight percent of the constituent monomers are acrylicmonomers and the remainder weight percent, if any, of the constituentmonomers are C₈ -C₁₂ monovinyl hydrocarbons, and a crosslinking agentselected from the groups consisting of dicarboxylic acids and anhydridesof dicarboxylic acids.
 6. A powder paint in accordance with claim 1wherein said particulate, organic, film-former consists essentially of acopolymer of monoethylenically unsaturated monomers of which about 5 toabout 20 weight percent are glycidyl esters of a monoethylenicallyunsaturated carboxylic acid, in excess of 50 weight percent of theconstituent monomers are esters of a C₁ -C₈ monohydric alcohol andacrylic or methacrylic acid and the remainder weight percent, if any, ofthe constituent monomers are C₈ -C₁₂ monovinyl hydrocarbons, and acrosslinking agent selected from the group consisting of dicarboxylicacids and anhydrides of dicarboxylic acids.
 7. A powder paint inaccordance with claim 1 wherein said copolymer of said particulate,organic, film-former bears functional groups provided by constituentmonomers which are selected from C₅ -C₇ monohydroxy acrylates and C₅ -C₇monohydroxy methacrylates and is employed with a melamine crosslinkingagent.
 8. A powder paint in accordance with claim 1 wherein saidaluminum flakes are encapsulated by dispersing 100 parts by weight ofaluminum flakes and about 10 to about 200 parts by weight of saidthermosettable, organic, film-former in a volatile solvent boiling inthe range of about 40°C. to about 152°C., that is fugitive from saidthermosettable, organic, film-former and said aluminum flakes in spraydrying and spray drying said dispersion, said solvent being present insaid dispersion in an amount in excess of the total amount of saidaluminum flakes and said film-former.
 9. A powder paint in accordancewith claim 8 wherein said 100 parts by weight of said aluminum flakes isdispersed in said solvent with about 30 to about 70 parts by weight ofsaid thermosettable, organic, film-former, and said solvent is selectedfrom methylene chloride, alcohols, ketones and hydrocarbons boiling inthe range of about 50°C. to about 90°C. and is present in saiddispersion in an amount at least 3 times the combined amounts of saidaluminum flakes and said film-former.
 10. A powder paint in accordancewith claim 1 wherein said aluminum flakes are encapsulated in athermosettable, organic, film-former consisting essentially of acopolymer of about 5 to about 20 weight percent of a glycidyl ester of amonoethylenically unsaturated carboxylic acid and about 80 to about 95weight percent of esters of a C₁ -C₈ monohydric alcohol and acrylic ormethacrylic acid and a crosslinking agent selected from the groupconsisting of dicarboxylic acids and anhydrides of dicarboxylic acids.11. A powder paint in accordance with claim 1 wherein said aluminumflakes are encapsulated in a thermosettable, organic, film-formerconsisting essentially of a copolymer of about 5 to about 20 weightpercent of a glycidyl ester of a monoethylenically unsaturatedcarboxylic acid, about 2 to about 10 weight percent of a C₅ -C₇ hydroxyacrylate or methacrylate and about 70 to about 93 weight percent ofesters of a C₁ -C₈ monohydric alcohol and acrylic or methacrylic acidand a crosslinking agent selected from the group consisting ofdicarboxylic acids and anhydrides of dicarboxylic acids.
 12. A powderpaint in accordance with claim 1 wherein said aluminum flakes areencapsulated in a thermosettable, organic, film-former consistingessentially of a copolymer of about 5 to about 20 weight percent of aglycidyl ester of a monoethylenically unsaturated carboxylic acid, about2 to about 10 weight percent of an alpha-beta olefinically unsaturatedamide and about 70 to about 93 weight percent of esters of a monohydricalcohol and acrylic or methacrylic acid and a crosslinking agentselected from the group consisting of dicarboxylic acids and anhydridesof dicarboxylic acids.
 13. A powder paint in accordance with claim 12wherein said alpha-beta olefinically unsaturated amide is selected fromthe group consisting of acrylamide and methacrylamide.
 14. A powderpaint in accordance with claim 1 wherein said particulate, organic,film-former consists essentially of a copolymer of about 5 to about 20weight percent of a glycidyl ester of a monoethylenically unsaturatedcarboxylic acid and about 80 to about 95 weight percent of esters of aC₁ -C₈ monohydric alcohol and acrylic or methacrylic acid and acrosslinking agent selected from the group consisting of dicarboxylicacids and anhydrides of dicarboxylic acids.
 15. A powder paint inaccordance with claim 1 wherein said particulate, organic, film-formerconsists essentially of a copolmer of a monoethylenically unsaturatedcarboxylic acid, about 2 to about 10 weight percent of a C₅ -C₇hydroxyacrylate or methacrylate and about 70 to about 93 weight percentof esters of a C₁ -C₈ monohydric alcohol and acrylic or methacrylic acidand a crosslinking agent selected from the group consisting ofdicarboxylic acids and anhydrides of dicarboxylic acids.
 16. A powderpaint in accordance with claim 1 wherein said particulate, organic,film-former consists essentially of a copolymer of a monoethylenicallyunsaturated carboxylic acid, about 2 to about 10 weight percent ofacrylamide or methacrylamide, and about 70 to about 93 weight percent ofesters of a C₁ -C₈ monohydric alcohol and acrylic or methacrylic acidand a crosslinking agent selected from the group consisting ofdicarboxylic acids and anhydrides of dicarboxylic acids.